Catálogo de publicaciones - revistas

<jats:title>Forking Replisomes</jats:title> <jats:p> Replisomes are multiprotein machines that replicate DNA. Significant insight into how they work comes from in vitro studies, but how replisomes are organized in living cells has remained unclear. <jats:bold> Reyes-Lamothe <jats:italic>et al.</jats:italic> </jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" page="498" related-article-type="in-this-issue" vol="328" xlink:href="10.1126/science.1185757">498</jats:related-article> ) have watched the replisome in living <jats:italic>Escherichia coli</jats:italic> cells using single-molecule fluorescence spectroscopy with millisecond time resolution. Cells expressing fluorescent derivatives of 10 different replisome components revealed both the stoichiometry and spatial distribution of the components at active replication forks in <jats:italic>Escherichia coli</jats:italic> . A similar technique could be used to study other molecular machines as they function. </jats:p>

<jats:title>Transcription and Translation in Train</jats:title> <jats:p> In bacteria, translation of messenger RNA into proteins by the ribosome usually begins soon after the ribosome binding site emerges from RNA polymerase. Now there is evidence for direct coupling between transcription and translation in bacteria. <jats:bold>Proshkin et al.</jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" page="504" related-article-type="in-this-issue" vol="328" xlink:href="10.1126/science.1184939">504</jats:related-article> ; see the Perspective by <jats:bold> <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="5977" page="436" related-article-type="in-this-issue" vol="328" xlink:href="10.1126/science.1189971">Roberts</jats:related-article> </jats:bold> ) show that the trailing ribosome controls the rate of transcription by preventing RNA polymerase from spontaneous backtracking, which allows precise adjustment of transcriptional yield to translational needs under various growth conditions. <jats:bold>Burmann et al.</jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" page="501" related-article-type="in-this-issue" vol="328" xlink:href="10.1126/science.1184953">501</jats:related-article> ; see the Perspective by <jats:bold> <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="5977" page="436" related-article-type="in-this-issue" vol="328" xlink:href="10.1126/science.1189971">Roberts</jats:related-article> </jats:bold> ) provide a potential mechanism for coupling by showing that the transcription factor NusG, which binds RNA polymerase through its amino-terminal domain, competitively binds either a ribosomal protein or the Rho transcription termination factor through its carboxy-terminal domain. Rho binding might occur after release of the ribosome from messenger RNA, thus linking termination of transcription and translation. </jats:p>

<jats:title>Transcription and Translation in Train</jats:title> <jats:p> In bacteria, translation of messenger RNA into proteins by the ribosome usually begins soon after the ribosome binding site emerges from RNA polymerase. Now there is evidence for direct coupling between transcription and translation in bacteria. <jats:bold>Proshkin et al.</jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" page="504" related-article-type="in-this-issue" vol="328" xlink:href="10.1126/science.1184939">504</jats:related-article> ; see the Perspective by <jats:bold> <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="5977" page="436" related-article-type="in-this-issue" vol="328" xlink:href="10.1126/science.1189971">Roberts</jats:related-article> </jats:bold> ) show that the trailing ribosome controls the rate of transcription by preventing RNA polymerase from spontaneous backtracking, which allows precise adjustment of transcriptional yield to translational needs under various growth conditions. <jats:bold>Burmann et al.</jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" page="501" related-article-type="in-this-issue" vol="328" xlink:href="10.1126/science.1184953">501</jats:related-article> ; see the Perspective by <jats:bold> <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="5977" page="436" related-article-type="in-this-issue" vol="328" xlink:href="10.1126/science.1189971">Roberts</jats:related-article> </jats:bold> ) provide a potential mechanism for coupling by showing that the transcription factor NusG, which binds RNA polymerase through its amino-terminal domain, competitively binds either a ribosomal protein or the Rho transcription termination factor through its carboxy-terminal domain. Rho binding might occur after release of the ribosome from messenger RNA, thus linking termination of transcription and translation. </jats:p>

<jats:title> HIV and <jats:italic>Salmonella</jats:italic> </jats:title> <jats:p> HIV-positive individuals who are infected with nontyphoidal strains of <jats:italic>Salmonella enterica</jats:italic> often succumb to high morbidity and mortality. Why this is the case is unknown. <jats:bold> MacLennan <jats:italic>et al.</jats:italic> </jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" page="508" related-article-type="in-this-issue" vol="328" xlink:href="10.1126/science.1180346">508</jats:related-article> ; see the Perspective by <jats:bold> <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="5977" page="439" related-article-type="in-this-issue" vol="328" xlink:href="10.1126/science.1189088"> <jats:bold>Moir and Fauci</jats:bold> </jats:related-article> </jats:bold> ) have uncovered a dysregulated antibody response to <jats:italic>Salmonella</jats:italic> that is the likely culprit. Sera from HIV-infected individuals do a poor job of killing <jats:italic>S.</jats:italic> Typhimurium, despite surprisingly elevated antibody titers. Experiments showed that HIV-infected serum inhibited the power of normal serum to kill <jats:italic>Salmonella</jats:italic> . Inhibition was specific to antibodies against lipopolysaccharide (LPS), a component of the cell wall of <jats:italic>Salmonella</jats:italic> . Hence, HIV-infected sera was able to kill <jats:italic>Salmonella</jats:italic> strains lacking LPS, and removing LPS immunoglobulin G from infected sera permitted <jats:italic>Salmonella</jats:italic> killing. Thus, not only does HIV cause defects in cell-mediated immunity but it also seems to impair humoral immunity, with severe consequences for multiple infections. </jats:p>

<jats:title>Reading Influences and Achievement</jats:title> <jats:p> When it comes to learning to read, children are immersed in a variety of influences. Debate rages over what aspects are affected and what importance to attribute to genetic influences, the effect of good teaching, the tools used, the family environment, and so on. <jats:bold> Taylor <jats:italic>et al.</jats:italic> </jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" page="512" related-article-type="in-this-issue" vol="328" xlink:href="10.1126/science.1186149">512</jats:related-article> ) analyzed reading achievement from kindergarten through to fifth grade in mono- and dizygotic twins from a diverse population. The results show that better teachers allow children to fulfill their genetic potential. </jats:p>

<jats:p>The show includes effects of teacher quality on early reading, Asian monsoon failure and megadrought, the National Ecological Observatory Network, and more.</jats:p>

<jats:p>A weekly roundup of information on newly offered instrumentation, apparatus, and laboratory materials of potential interest to researchers.</jats:p>